The main purpose of the proposed research is to improve measurement of drug abuse prevention through the use of a new scaling model for longitudinal data. The use of this new scaling model will allow the researcher to build scales uniquely sensitive to change in a construct over time. Dynamic constructs, constructs that change as a function of time, are quite common in drug abuse prevention research. Such constructs as drug use onset and the psychosocial correlates of onset are variables that develop over time, particularly in populations of young people. Typically dynamic constructs have been measured using scaling models developed for static constructs, because such models have been the only ones available. However, recently a new scaling model has been developed especially for dynamic constructs measured longitudinally. The use of this scaling model will result in greater measurement precision and thus increased statistical power in prevention research. The proposed research has several goals. First is the refinement of a family of consistency indices recently proposed for the new longitudinal scaling model. The improvement of these indices will improve researchers' judgments about the degree to which the scaling model fits observed data. Second, the proposed research will construct relevant significance test. Third, these newly developed tools will be used to examine existing drug abuse prevention data for longitudinal scales. Fourth, the proposed research will see the extent to which the obtained scales replicate across demographic variables such as sex and ethnicity.